Heretofore on most automobiles and vehicles, the operation of windshield wipers is normally by manually switching them on and off. Furthermore, the controls normally require manually switching between the various settings for varying the speed of operation for the wiper. While in many instances such is a satisfactory mode of operation, oftentimes, the operator of the vehicle will forget to change the speed of operation of the wiper when the intensity of the rain changes or stops.
The above systems heretofore used in vehicles require the operator's personal attention each time a change in the operation of the wipers is required.
Attempts have been made to provide automatic control apparatus for controlling the operation of the windshield wipers. One such system is disclosed in U.S. Pat. No. 4,355,271 wherein an infrared radiating device directs infrared radiation from the interior of the vehicle through the wind screen to be reflected from the outer surface of the wind screen back into the vehicle where it is detected by a detector. The apparatus is responsive to variations in infrared radiation incident upon the detector to control the wiper apparatus to set the vehicle wipers in operation when dust or water is detected on the wind screen. One apparent problem with such a device is that it can be triggered by dust as well as rain.
Another windshield wiper control is disclosed in U.S. Pat. No. 4,317,073 wherein a plurality of sensors, which are activated in response to various degrees of moisture precipitation or rain, are used to start and stop the wiper mechanism associated with a windshield wiper and also to operate it intermittently and at a low or high speed in accordance with the degree of rain or moisture of precipitation. Typical moisture sensors utilized with such an apparatus are optical sensors or thermistors. The patent also teaches the use of electrode type sensors.
Examples of other systems for automatically controlling the operation of a windshield wiper motor are disclosed in U.S. Pat. Nos. 3,786,330--3,826,979--4,131,834--4,010,383--4,339,698--3,649,898, and British Pat. No. 1,101,441 granted on Jan. 31, 1968.